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# -*- coding: utf-8 -*-
"""
Bimap - bidirectional mapping between code/value
"""
class BimapError(Exception):
pass
class Bimap(object):
"""
Bi-directional mapping between code/text.
Initialised using:
name: Used for exceptions
dict: Dict mapping from code (numeric) to text
error: Error type to raise if key not found
The class provides:
* A 'forward' map (code->text) which is accessed through
__getitem__ (bimap[code])
* A 'reverse' map (code>value) which is accessed through
__getattr__ (bimap.text)
* A 'get' method which does a forward lookup (code->text)
and returns a textual version of code if there is no
explicit mapping (or default provided)
>>> class TestError(Exception):
... pass
>>> TEST = Bimap('TEST',{1:'A', 2:'B', 3:'C'},TestError)
>>> TEST[1]
'A'
>>> TEST.A
1
>>> TEST.X
Traceback (most recent call last):
...
TestError: TEST: Invalid reverse lookup: [X]
>>> TEST[99]
Traceback (most recent call last):
...
TestError: TEST: Invalid forward lookup: [99]
>>> TEST.get(99)
'99'
"""
def __init__(self,name,forward,error=KeyError):
self.name = name
self.error = error
self.forward = forward.copy()
self.reverse = dict([(v,k) for (k,v) in list(forward.items())])
def get(self,k,default=None):
try:
return self.forward[k]
except KeyError as e:
return default or str(k)
def __getitem__(self,k):
try:
return self.forward[k]
except KeyError as e:
raise self.error("%s: Invalid forward lookup: [%s]" % (self.name,k))
def __getattr__(self,k):
try:
return self.reverse[k]
except KeyError as e:
raise self.error("%s: Invalid reverse lookup: [%s]" % (self.name,k))
if __name__ == '__main__':
import doctest
doctest.testmod()
|
